I’m flying up to 30 miles in calm weather with an FMS Fox 3000 on a 6s 10,000 mAh lipo. Calling everyone’s advice on increasing range.Upgraded the prop to a 13x13 carbon. Flew 40 minutes yesterday. I am aware of building custom lithium ion packs from 18650 cells. Any advice on motor setup? E-Flite Power 52 or 60? Lower kV better for efficiency? I’m debating running 4 or 5 cells, as 6 cell gives way too much headroom for easy cruising. Is it best to run the motor on a lower cell count and higher throttle? It is my current understanding that most BLDC motors run most efficiently between 75% to 85% throttle, which tells me full throttle should provide just barely enough thrust for takeoff. Right now the plane is cruising at 55%ish throttle and that can’t be very good as the ESC is wasting more energy in the form of heat, right?
Please any recommendations help tremendously!
Here is the video:
I recently acquired a Cube orange with ADS-B, have not installed yet, but the old 3DR PX4 is still running like a charm!
“I am aware of building custom lithium ion packs from 18650 cells”
You better be using Samsung INR21700-40T 4000mAh - 35A. 21700 cells have more energy per gramm.
“I’m debating running 4 or 5 cells”
In theory there should be no difference. With bigger voltage the plane will cruise at lower throttle value. In practice it is hard to predict. Difference will be negligible.
" It is my current understanding that most BLDC motors run most efficiently between 75% to 85% throttle"
I am not sure about this. Motors are pretty efficient insude all working range, it is the props that affect efficiency at differents speeds.
“Is it best to run the motor on a lower cell count and higher throttle?”
No, not really gonna make a difference.
“Right now the plane is cruising at 55%ish throttle and that can’t be very good as the ESC is wasting more energy in the form of heat, right?”
No. Esc is just a bunch of MOSFETs that are PWMing over the H-bridge. It does not waste more heat at 55%. ESCs are pretty efficient, you should look at other components to find the potential to increase.
Regarding the motor+prop combo. It is hard to give an advice which us the best because it vary plane to plane with different flight mass and cruise speed. You just have to experiment with different props and motor to find best combo for this plane.
For your setup I think the biggest boost in range will be by utilizing INR21700-40T, leave motor and prop as is, just get better battery. 4 or 5 or 6 cells? I would choose 6s because this is what you already have. It would be easyer to compare with you current setup if LiIon batery has the same cell count.
Is it generally better to underpower electric motors for slow cruising? Smaller electric motors usually require a lower voltage and this allows the pack capacity to increase per a given weight.
I’m debating between an E-Flite power 46, 52, and 60. I want the absolute least power consumption, and ideally no more power than required for takeoff. I currently takeoff with 75% throttle on 6s with a 13x13 and cheap FMS power 60 motor. I do not want to run more than 5s, it is unnecessary for my application. The power 46 has a higher kV so I could potentially run it on 4s, but the plane might be lethargic on takeoffs. Of course, I can manage if there will be a tradeoff for lower current draw.
2.9 pounds. I’m reading others achieving 2 plus hours with their fixed wings and I only have 50 minutes at best with a 3 meter span. There is certainly something I’m doing poorly.
2.9 pounds = 1315g
INR21700-40T = 4000 mAh Weight: 66.8 g
1315/67=19.6 We could have 20 li-ion batteries with same mass. Lets assume 4 in parallel 5 s.
5s4p battery with capacity of 4000*4=16Ah
You can have 5s 16Ah battery with the same mass as you have now.
" I’m reading others achieving 2 plus hours with their fixed wings and I only have 50 minutes"
Maybe those guys have better battery, or maybe they are flying in Loiter mode with zero change in altitude. And you fly manually, change speed and altitute all the time and loose energy.
Usually those time and speed records are done in automatic modes.
If you watch the video it is fully Auto. I will be flying again late this afternoon with a more conservative trim throttle due to extra calm conditions. Most of the flight path is BVLOS and there is only short range telemetry at the moment. Here is the HD version video link: https://youtu.be/HxW6N-4ybxg
I researched that the Panasonic NCR series is really good but perhaps that is outdated by the 21700s.
Do I increase range by increasing battery weight? Seems like this plane can take another 2 pounds easily. It has zero problem climbing fast right now. I’ve taken it to 8,500 ft AGL on the existing lipo. more weight would increase the max efficient cruise speed which is ideal for range.
If the plane can handle extra weight then yes extra battery means more flight time, but of course this is a bell shaped curve, after some weight the efficiency will drop, look at the forum fo your plane what is maximum recomended mass… Add rock to your plane to see how current draw changes with extra load. Then by 21700’s for the mass of current battery and rocks. use my calculation to see how many of them you can handle.